Research
Original Investigation | HEALTH CARE REFORM
Outpatient Care Patterns and Organizational Accountability in Medicare J. Michael McWilliams, MD, PhD; Michael E. Chernew, PhD; Jesse B. Dalton, MA; Bruce E. Landon, MD, MBA, MSc
IMPORTANCE Fostering accountability in the Medicare Accountable Care Organization (ACO) programs may be challenging because traditional Medicare beneficiaries have unrestricted choice of health care providers, are attributed to ACOs based on utilization, and often receive fragmented care.
Invited Commentary page 945 Supplemental content at jamainternalmedicine.com
OBJECTIVE To measure 3 related constructs relevant to ACO incentives and their capacity to manage care: stability of patient assignment, leakage of outpatient care, and contract penetration. DESIGN, SETTING, AND PARTICIPANTS Using 2010-2011 Medicare claims and rosters of physicians in organizations participating in ACO programs, we examined these constructs among 524 246 beneficiaries hypothetically assigned to 145 ACOs prior to the start of the Medicare ACO programs. We compared estimates by patient complexity, ACO size, and the primary care orientation of ACO specialty mix. MAIN OUTCOMES AND MEASURES Three related construct measurements: stability of assignment, defined as the proportion of patients whose assignment to an ACO in 2010 was unchanged in 2011; leakage of outpatient care, defined as the proportion of office visits for an assigned population that occurred outside of the contracting organization; and contract penetration, defined as the proportion of Medicare outpatient spending billed by an ACO that was devoted to assigned patients. RESULTS Of beneficiaries assigned to an ACO in 2010, 80.4% were assigned to the same ACO in 2011. Of those assigned to an ACO in 2010 or 2011, 66.0% were consistently assigned in both years. Unstable assignment was more common among beneficiaries with fewer conditions and office visits but also among those in several high-cost categories, including the highest decile of per-beneficiary spending. Among ACO-assigned beneficiaries, 8.7% of office visits with primary care physicians were provided outside of the assigned ACO, and 66.7% of office visits with specialists were provided outside of the assigned ACO. Leakage of outpatient specialty care was greater for higher-cost beneficiaries and substantial even among specialty-oriented ACOs (54.6% for lowest quartile of primary care orientation). Of Medicare spending on outpatient care billed by ACO physicians, 37.9% was devoted to assigned beneficiaries. This proportion was higher for ACOs with greater primary care orientation (60.0% for highest quartile vs 33.6% for lowest). CONCLUSIONS AND RELEVANCE Care patterns among beneficiaries served by ACOs suggest distinct challenges in achieving organizational accountability in Medicare. Continued monitoring of these patterns may be important to determine the regulatory need for enhancing ACOs’ incentives and their ability to improve care efficiency.
JAMA Intern Med. 2014;174(6):938-945. doi:10.1001/jamainternmed.2014.1073 Published online April 21, 2014. 938
Author Affiliations: From the Department of Health Care Policy, Harvard Medical, Boston, Massachusetts (McWilliams, Chernew, Dalton, Landon); Division of General Internal Medicine and Primary Care, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts (McWilliams); Division of General Internal Medicine and Primary Care, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts (Landon). Corresponding Author: J. Michael McWilliams, MD, PhD, Department of Health Care Policy, Harvard Medical School, 180 Longwood Ave, Boston, MA 02115 ([email protected]). jamainternalmedicine.com
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Enhancing Organizational Accountability in Medicare
T
o foster greater accountability in the traditional fee-forservice (FFS) Medicare program, the Medicare Accountable Care Organization (ACO) programs reward participating health care provider groups that achieve slower spending growth and high quality of care. Concerns have been raised, however, that features of the programs may weaken these incentives and undermine ACO efforts to manage care.1 Specifically, unrestricted choice of health care providers is maintained for beneficiaries in the ACO programs. Furthermore, Medicare must rely on utilization patterns to attribute patients to ACOs because traditional Medicare beneficiaries are not required to select a primary care physician (PCP). To characterize the potential challenges posed by the Medicare ACO model when applied to outpatient care that is often fragmented and unstable, 2 we examined 3 related constructs: (1) stability of assignment, defined as the proportion of patients assigned to an ACO in one year that remains assigned to the same ACO in the subsequent year; (2) leakage of outpatient care, defined as the proportion of office visits for an ACO’s assigned patients that occurs outside of the contracting organization; and (3) contract penetration, defined as the proportion of Medicare outpatient spending billed by the contracting organization that is devoted to assigned patients. These factors may be important determinants of ACO incentives and the ability of ACOs to improve care efficiency. Stability in patient assignment increases future returns on patientspecific investments in care management. Leakage of outpatient care increases the costs of care coordination and diminishes the reach of ACO influence. Greater contract penetration enhances incentives for ACOs to implement systemic changes that affect all Medicare beneficiaries they serve. Using 2010-2011 Medicare claims and rosters of ACO physicians, we quantified stability of assignment, leakage of outpatient care, and contract penetration for 145 ACOs at baseline, prior to the start of the Medicare ACO programs. We compared estimates by patient complexity because unstable assignment and leakage among high-cost groups may be of particular concern to ACOs. We also compared estimates by organizational size and specialty mix to describe the incentives and challenges faced by different types of ACOs.
Methods Our study was approved by the Harvard Medical School Committee on Human Studies and the Privacy Board of the Centers for Medicare & Medicaid Services (CMS).
Assignment of Beneficiaries to ACOs The CMS requires ACOs to post online lists of all health care providers included in ACO contracts (hereinafter referred to as ACO contracting networks); contracts may include only subsets of organizations’ constituent practices or physicians.3 From ACO websites or officials, we obtained lists of physicians making up the ACO contracting networks for 145 of the 252 organizations entering the Medicare Shared Savings Program (SSP) or Pioneer ACO program in 2012 or 2013, including 28 (88%) of the 32 Pioneer ACOs and 75 (66%) of the 114 SSP ACOs enjamainternalmedicine.com
Original Investigation Research
tering in 2012. The ACOs excluded from our study had not posted lists of contracting physicians at the time of our data collection and tend to be smaller. We converted 95.6% of physician names to National Provider Identifiers (NPIs) using the CMS NPI Registry.4 Following the Medicare SSP rules for beneficiary assignment5 and using 2010-2011 Medicare claims for a random 20% sample of beneficiaries, we attributed each beneficiary in each year to 1 of the 145 ACOs if the ACO (defined by the NPIs included in its contracting network) accounted for more spending for outpatient primary care services (Current Procedural Terminology [CPT] codes 99201-15, G0402, and G0438-9 for outpatient office visits) than any other ACO or tax identification number present in claims (eAppendix in the Supplement). We used assignment rules from the SSP because it is much larger than the Pioneer program, particularly after the departure of 9 ACOs from the Pioneer program in 2013 and the addition of 123 ACOs to the SSP in 2014.6,7 Per the 2-step SSP assignment algorithm, beneficiaries receiving at least 1 primary care service from a PCP (defined by specialty codes for general practice, family practice, internal medicine, or geriatric medicine) were assigned based on primary care services provided by PCPs. Beneficiaries receiving no primary care services from a PCP were assigned based on primary care services provided by physicians of other specialties, nurse practitioners, or physician assistants. Beneficiaries receiving no primary care services were not assigned. Importantly, these assignments were hypothetical because the ACO programs did not begin until 2012. For reasons detailed in the eAppendix in the Supplement, we focused on outpatient primary care services when assigning beneficiaries and excluded other services (eg, physician visits in nursing facilities) that also are considered primary care services by SSP assignment rules (eTable 1 in the Supplement).8 In a sensitivity analysis including these other services in the assignment algorithm, assignment of highcost beneficiaries to ACOs was slightly less stable than we report (eTable 2 in the Supplement).
Study Population Our study included 524 246 beneficiaries who were continuously enrolled in traditional fee-for-service Medicare in both 2010 and 2011 (ie, no enrollment in Medicare Advantage managed care plans), lived in the same county in both years, and were assigned to 1 of the 145 ACOs in either year. Most of our analyses focused on the 430 658 beneficiaries who were assigned to an ACO in 2010. Because assignment to an ACO in a given year requires at least 1 primary care service in that year, our study excluded beneficiaries with no primary care services in both years.
Study Variables Stability of Assignment Among beneficiaries assigned to an ACO in 2010, we calculated the proportion assigned to the same ACO in 2011 rather than to a different health care provider group or no health care provider (unassigned). Among beneficiaries assigned to an ACO in 2010 or 2011, we also calculated the proportion assigned to the same ACO in both years. JAMA Internal Medicine June 2014 Volume 174, Number 6
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Leakage of Outpatient Care Using 2010 claims, we calculated the percentage of all outpatient primary care services provided to beneficiaries assigned to an ACO that were not provided by ACO physicians. We focused on leakage of these commonly billed office visits with PCPs and specialists (defined as non-PCP physicians) as a proxy for an ACO’s potential direct influence over outpatient testing and procedures, preventive care, and recommendations for elective hospitalization and emergency care. We did not analyze leakage of inpatient care because we could not reliably measure the extent to which independent physician groups provide or influence inpatient care at hospitals to which they admit patients. The network of physicians included in an ACO contract is often a subset of the participating organization’s member physicians. To recognize care provided within the larger organization but not necessarily within the ACO contracting network, we used American Medical Association (AMA) Group Practice data describing organizational membership (updated through 2011) for 90% of PCPs and 81% of medical and surgical specialists in the AMA Physician Masterfile who practice in groups of 3 or more physicians and billed for office visits in 2009 Medicare claims.9,10 For each of the 145 ACOs, we assembled NPIs from all groups in the AMA Group Practice File with names matching the organization or one of its constituent parts (enumerated from organizational websites) into a single inclusive group of NPIs. In each organization’s physician membership, we also included NPIs not recognized by the Group Practice File but whose most frequently appearing tax identification number in claims for office visits was shared by NPIs identified as ACO members (eAppendix in the Supplement). For 23 ACOs whose constituent practices were not consistently found in the Group Practice File, we obtained physician directories describing the organizations’ full physician membership directly from the organizations or their websites. When measuring leakage for each ACO, we considered both physicians listed in the ACO’s contracting network and additional member physicians identified by these methods as part of the participating organization. Combined, these methods increased the total number of physicians recognized as members of organizations participating in ACO programs by 43.9% relative to the ACO contracting networks alone (74 201 vs 51 563) and by 58.7% among physicians billing for office visits; 71.3% of the additional NPIs were specialists, suggesting disproportionate inclusion of PCPs in ACO contracting networks by multispecialty organizations. We calculated leakage rates both for primary care services provided specifically by PCPs and for the same set of office visits (CPT codes 99201-15, G0402, and G0438-9) provided by specialists. Of note, after the elimination of separate billing codes for outpatient specialty consultations effective January 2010, these consultations have been billed as office visits and are thus captured by this set of codes.11 Contract Penetration For each ACO, we summed all spending in 2010, including coinsurance amounts, for all services delivered in outpatient settings that were billed by ACO physicians (eAppendix in the Supplement). We then calculated the proportion of this spend940
ing that was devoted to beneficiaries assigned to the ACO as opposed to other beneficiaries receiving outpatient care from the ACO. To better reflect incentives for systemic changes in care delivery at the organizational level, we considered all of an organization’s member physicians, not just those included in its ACO contract, when assigning beneficiaries and totaling spending for the purpose of this measure. A sensitivity analysis using ACO contracting networks for this measure produced similar results. Patient Complexity and Per-Beneficiary Spending From Medicare enrollment files, we determined disability as the original reason for Medicare eligibility, presence of endstage renal disease, and receipt of Medicaid benefits. For each of 25 conditions in the Chronic Condition Warehouse,12 we determined if beneficiaries had been diagnosed with the condition before 2010. We also assessed total annual perbeneficiary spending in 2010 and 2011 for all services covered by Parts A and B of Medicare and the number of office visits for each beneficiary in 2010. Organizational Size and Primary Care Orientation We created 3 size categories for ACOs based on the number of assigned beneficiaries: (1) fewer than 2000 (or 45% of office visits provided by specialists). As detailed in Table 3, stability of assignment and leakage of office visits with PCPs varied considerably among ACOs but differed minimally by ACO size. Assignments were more stable for ACOs with greater primary care orientation. As expected, JAMA Internal Medicine June 2014 Volume 174, Number 6
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Table 2. Stability of Assignment and Leakage of Outpatient Care Among Medicare Beneficiaries Assigned to an ACO in 2010, Stratified by Beneficiary Characteristics Stability of Assignment
Leakage of Outpatient Care in 2010
Beneficiaries, No.
Assigned to Same ACO in 2010 and 2011
Office Visitsb With PCPs
430 658
80.4
8.7
66.7
0-2
93 944
73.4
7.8
63.1
3-5
149 179
82.2
7.9
65.9
6-8
116 642
82.9
8.8
67.0
≥9
70 893
81.9
10.2
68.9
Characteristic All beneficiaries assigned to an ACO in 2010
Office Visitsb With Specialists
CCW conditions present by 2010, No.
End-stage renal disease present by 2010 Yes
3978
69.3
11.1
61.0
No
426 680
80.5
8.7
66.8
Yes
86 409
75.3
10.6
65.7c
No
344 249
81.7
8.2
66.9c
Yes
79 143
76.4
10.7
67.5c
No
351 515
81.3
8.1
66.5c
Disability as original reason for Medicare eligibility
Medicaid recipient in 2010
Total spending in 2010 Lowest quartile
99 646
77.8
4.4
54.3
Quartile 2
111 083
82.5
6.7
64.2
Quartile 3
111 092
81.9
8.9
68.0
Highest quartile
108 837
79.1
11.3
68.1
42 909
76.6
11.9
67.5
Highest decile Office visitsb in 2010 With PCPs, No. 0
44 793
53.4
NA
32.6
1-2
124 521
76.4
4.1
70.9
3-5
147 185
86.7
6.7
71.4
≥6
114 159
87.2
10.5
71.6
0
64 078
82.0
5.1
NA
1-2
94 834
78.5
7.3
61.1
3-5
104 054
81.1
8.3
64.4
≥6
167 692
80.4
10.5
67.5
1-2
49 300
66.7
2.6
25.7
3-5
96 100
79.3
4.9
55.5
≥6
285 258
83.1
9.4
67.9
Abbreviations: ACO, Accountable Care Organization; CCW, Chronic Condition Warehouse; CPT, Current Procedural Terminology; NA, not applicable; PCP, primary care physician. a
Unless otherwise noted, data are reported as percentage of beneficiaries (stability) or office visits (leakage) among beneficiaries in the row category.
b
Outpatient primary care services as defined by rules for beneficiary attribution in the Medicare Shared Savings and Pioneer Program (CPT codes 99201-15, G0402, and G0438-9) .
c
Differences across beneficiary categories not statistically significant (P ⱖ .05).
With specialists, No.
With PCPs or specialists, No.
leakage of office visits with specialists was greater for smaller than larger ACOs (77.7% vs 63.6% [P < .001]) and for ACOs with specialty mixes oriented more toward primary care (95.6% for the highest quartile of primary care orientation vs 54.6% for the lowest quartile [P < .001]). Of Medicare spending on outpatient care billed by ACO physicians, 37.9% was devoted to ACO-assigned beneficiaries, varying from 24.6% at the 10th percentile of ACOs to 65.6% at the 90th percentile. This proportion varied minimally with size and was substantially higher for ACOs with specialty mixes oriented more toward primary care (60.0% for the highest quartile of primary care orientation vs 33.6% for the lowest quartile [P < .001]). 942
Discussion In this study of 145 organizations participating in the Medicare ACO programs, over one-third of beneficiaries attributed to an ACO in 2010 or 2011 was not assigned to the same ACO in both years. Thus, in any given year, a substantial share of patients for whom an ACO is held accountable may be newly or transiently assigned. Although healthy beneficiaries using little primary care contributed to this instability, unstably assigned beneficiaries were more likely than stably assigned beneficiaries to be in several high-cost
JAMA Internal Medicine June 2014 Volume 174, Number 6
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jamainternalmedicine.com
Enhancing Organizational Accountability in Medicare
Original Investigation Research
Table 3. Stability of Assignment, Leakage of Outpatient Care, and Contract Penetration Among ACOs With Specific Characteristicsa Stability of Assignment
Characteristic
ACOs, No.
Total
145
Leakage of Outpatient Care in 2010
Contract Penetration in 2010
Proportion of Patients Assigned to ACO in 2010 That Was Assigned to Same ACO in 2011
Office Visitsb With PCPs
Office Visitsb With Specialists
Proportion of Medicare Outpatient Spending Billed by ACO in 2010 That Was Devoted to Assigned Patients
80.4 (73.1, 77.1-84.3, 87.2)
8.7 (4.9, 6.7-10.3, 13.7)
66.7 (38.4, 56.7-89.9, 97.2)
37.9 (24.6, 33.2-55.2, 65.6)
Abbreviations: ACO, Accountable Care Organization; CPT, Current Procedural Terminology; IQR, interquartile range; PCP, primary care physician. a
Unless otherwise noted, data are reported as overall percentage (distribution across ACOs: 10th percentile, IQR, 90th percentile) of beneficiaries (stability), office visits (leakage), or spending (contract penetration) among ACOs in the row category.
b
Outpatient primary care services as defined by rules for beneficiary attribution in the Medicare Shared Savings and Pioneer Program (CPT codes 99201-15, G0402, and G0438-9).
c
Size categories by number of assigned beneficiaries are scaled to the entire traditional Medicare population.
d
Differences across beneficiary categories not statistically significant (P ⱖ .05).
e
Percentage of ACO office visits, as defined in footnote b, provided by PCPs.
Sizec Small,
Original Investigation | HEALTH CARE REFORM
Outpatient Care Patterns and Organizational Accountability in Medicare J. Michael McWilliams, MD, PhD; Michael E. Chernew, PhD; Jesse B. Dalton, MA; Bruce E. Landon, MD, MBA, MSc
IMPORTANCE Fostering accountability in the Medicare Accountable Care Organization (ACO) programs may be challenging because traditional Medicare beneficiaries have unrestricted choice of health care providers, are attributed to ACOs based on utilization, and often receive fragmented care.
Invited Commentary page 945 Supplemental content at jamainternalmedicine.com
OBJECTIVE To measure 3 related constructs relevant to ACO incentives and their capacity to manage care: stability of patient assignment, leakage of outpatient care, and contract penetration. DESIGN, SETTING, AND PARTICIPANTS Using 2010-2011 Medicare claims and rosters of physicians in organizations participating in ACO programs, we examined these constructs among 524 246 beneficiaries hypothetically assigned to 145 ACOs prior to the start of the Medicare ACO programs. We compared estimates by patient complexity, ACO size, and the primary care orientation of ACO specialty mix. MAIN OUTCOMES AND MEASURES Three related construct measurements: stability of assignment, defined as the proportion of patients whose assignment to an ACO in 2010 was unchanged in 2011; leakage of outpatient care, defined as the proportion of office visits for an assigned population that occurred outside of the contracting organization; and contract penetration, defined as the proportion of Medicare outpatient spending billed by an ACO that was devoted to assigned patients. RESULTS Of beneficiaries assigned to an ACO in 2010, 80.4% were assigned to the same ACO in 2011. Of those assigned to an ACO in 2010 or 2011, 66.0% were consistently assigned in both years. Unstable assignment was more common among beneficiaries with fewer conditions and office visits but also among those in several high-cost categories, including the highest decile of per-beneficiary spending. Among ACO-assigned beneficiaries, 8.7% of office visits with primary care physicians were provided outside of the assigned ACO, and 66.7% of office visits with specialists were provided outside of the assigned ACO. Leakage of outpatient specialty care was greater for higher-cost beneficiaries and substantial even among specialty-oriented ACOs (54.6% for lowest quartile of primary care orientation). Of Medicare spending on outpatient care billed by ACO physicians, 37.9% was devoted to assigned beneficiaries. This proportion was higher for ACOs with greater primary care orientation (60.0% for highest quartile vs 33.6% for lowest). CONCLUSIONS AND RELEVANCE Care patterns among beneficiaries served by ACOs suggest distinct challenges in achieving organizational accountability in Medicare. Continued monitoring of these patterns may be important to determine the regulatory need for enhancing ACOs’ incentives and their ability to improve care efficiency.
JAMA Intern Med. 2014;174(6):938-945. doi:10.1001/jamainternmed.2014.1073 Published online April 21, 2014. 938
Author Affiliations: From the Department of Health Care Policy, Harvard Medical, Boston, Massachusetts (McWilliams, Chernew, Dalton, Landon); Division of General Internal Medicine and Primary Care, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts (McWilliams); Division of General Internal Medicine and Primary Care, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts (Landon). Corresponding Author: J. Michael McWilliams, MD, PhD, Department of Health Care Policy, Harvard Medical School, 180 Longwood Ave, Boston, MA 02115 ([email protected]). jamainternalmedicine.com
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Enhancing Organizational Accountability in Medicare
T
o foster greater accountability in the traditional fee-forservice (FFS) Medicare program, the Medicare Accountable Care Organization (ACO) programs reward participating health care provider groups that achieve slower spending growth and high quality of care. Concerns have been raised, however, that features of the programs may weaken these incentives and undermine ACO efforts to manage care.1 Specifically, unrestricted choice of health care providers is maintained for beneficiaries in the ACO programs. Furthermore, Medicare must rely on utilization patterns to attribute patients to ACOs because traditional Medicare beneficiaries are not required to select a primary care physician (PCP). To characterize the potential challenges posed by the Medicare ACO model when applied to outpatient care that is often fragmented and unstable, 2 we examined 3 related constructs: (1) stability of assignment, defined as the proportion of patients assigned to an ACO in one year that remains assigned to the same ACO in the subsequent year; (2) leakage of outpatient care, defined as the proportion of office visits for an ACO’s assigned patients that occurs outside of the contracting organization; and (3) contract penetration, defined as the proportion of Medicare outpatient spending billed by the contracting organization that is devoted to assigned patients. These factors may be important determinants of ACO incentives and the ability of ACOs to improve care efficiency. Stability in patient assignment increases future returns on patientspecific investments in care management. Leakage of outpatient care increases the costs of care coordination and diminishes the reach of ACO influence. Greater contract penetration enhances incentives for ACOs to implement systemic changes that affect all Medicare beneficiaries they serve. Using 2010-2011 Medicare claims and rosters of ACO physicians, we quantified stability of assignment, leakage of outpatient care, and contract penetration for 145 ACOs at baseline, prior to the start of the Medicare ACO programs. We compared estimates by patient complexity because unstable assignment and leakage among high-cost groups may be of particular concern to ACOs. We also compared estimates by organizational size and specialty mix to describe the incentives and challenges faced by different types of ACOs.
Methods Our study was approved by the Harvard Medical School Committee on Human Studies and the Privacy Board of the Centers for Medicare & Medicaid Services (CMS).
Assignment of Beneficiaries to ACOs The CMS requires ACOs to post online lists of all health care providers included in ACO contracts (hereinafter referred to as ACO contracting networks); contracts may include only subsets of organizations’ constituent practices or physicians.3 From ACO websites or officials, we obtained lists of physicians making up the ACO contracting networks for 145 of the 252 organizations entering the Medicare Shared Savings Program (SSP) or Pioneer ACO program in 2012 or 2013, including 28 (88%) of the 32 Pioneer ACOs and 75 (66%) of the 114 SSP ACOs enjamainternalmedicine.com
Original Investigation Research
tering in 2012. The ACOs excluded from our study had not posted lists of contracting physicians at the time of our data collection and tend to be smaller. We converted 95.6% of physician names to National Provider Identifiers (NPIs) using the CMS NPI Registry.4 Following the Medicare SSP rules for beneficiary assignment5 and using 2010-2011 Medicare claims for a random 20% sample of beneficiaries, we attributed each beneficiary in each year to 1 of the 145 ACOs if the ACO (defined by the NPIs included in its contracting network) accounted for more spending for outpatient primary care services (Current Procedural Terminology [CPT] codes 99201-15, G0402, and G0438-9 for outpatient office visits) than any other ACO or tax identification number present in claims (eAppendix in the Supplement). We used assignment rules from the SSP because it is much larger than the Pioneer program, particularly after the departure of 9 ACOs from the Pioneer program in 2013 and the addition of 123 ACOs to the SSP in 2014.6,7 Per the 2-step SSP assignment algorithm, beneficiaries receiving at least 1 primary care service from a PCP (defined by specialty codes for general practice, family practice, internal medicine, or geriatric medicine) were assigned based on primary care services provided by PCPs. Beneficiaries receiving no primary care services from a PCP were assigned based on primary care services provided by physicians of other specialties, nurse practitioners, or physician assistants. Beneficiaries receiving no primary care services were not assigned. Importantly, these assignments were hypothetical because the ACO programs did not begin until 2012. For reasons detailed in the eAppendix in the Supplement, we focused on outpatient primary care services when assigning beneficiaries and excluded other services (eg, physician visits in nursing facilities) that also are considered primary care services by SSP assignment rules (eTable 1 in the Supplement).8 In a sensitivity analysis including these other services in the assignment algorithm, assignment of highcost beneficiaries to ACOs was slightly less stable than we report (eTable 2 in the Supplement).
Study Population Our study included 524 246 beneficiaries who were continuously enrolled in traditional fee-for-service Medicare in both 2010 and 2011 (ie, no enrollment in Medicare Advantage managed care plans), lived in the same county in both years, and were assigned to 1 of the 145 ACOs in either year. Most of our analyses focused on the 430 658 beneficiaries who were assigned to an ACO in 2010. Because assignment to an ACO in a given year requires at least 1 primary care service in that year, our study excluded beneficiaries with no primary care services in both years.
Study Variables Stability of Assignment Among beneficiaries assigned to an ACO in 2010, we calculated the proportion assigned to the same ACO in 2011 rather than to a different health care provider group or no health care provider (unassigned). Among beneficiaries assigned to an ACO in 2010 or 2011, we also calculated the proportion assigned to the same ACO in both years. JAMA Internal Medicine June 2014 Volume 174, Number 6
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Leakage of Outpatient Care Using 2010 claims, we calculated the percentage of all outpatient primary care services provided to beneficiaries assigned to an ACO that were not provided by ACO physicians. We focused on leakage of these commonly billed office visits with PCPs and specialists (defined as non-PCP physicians) as a proxy for an ACO’s potential direct influence over outpatient testing and procedures, preventive care, and recommendations for elective hospitalization and emergency care. We did not analyze leakage of inpatient care because we could not reliably measure the extent to which independent physician groups provide or influence inpatient care at hospitals to which they admit patients. The network of physicians included in an ACO contract is often a subset of the participating organization’s member physicians. To recognize care provided within the larger organization but not necessarily within the ACO contracting network, we used American Medical Association (AMA) Group Practice data describing organizational membership (updated through 2011) for 90% of PCPs and 81% of medical and surgical specialists in the AMA Physician Masterfile who practice in groups of 3 or more physicians and billed for office visits in 2009 Medicare claims.9,10 For each of the 145 ACOs, we assembled NPIs from all groups in the AMA Group Practice File with names matching the organization or one of its constituent parts (enumerated from organizational websites) into a single inclusive group of NPIs. In each organization’s physician membership, we also included NPIs not recognized by the Group Practice File but whose most frequently appearing tax identification number in claims for office visits was shared by NPIs identified as ACO members (eAppendix in the Supplement). For 23 ACOs whose constituent practices were not consistently found in the Group Practice File, we obtained physician directories describing the organizations’ full physician membership directly from the organizations or their websites. When measuring leakage for each ACO, we considered both physicians listed in the ACO’s contracting network and additional member physicians identified by these methods as part of the participating organization. Combined, these methods increased the total number of physicians recognized as members of organizations participating in ACO programs by 43.9% relative to the ACO contracting networks alone (74 201 vs 51 563) and by 58.7% among physicians billing for office visits; 71.3% of the additional NPIs were specialists, suggesting disproportionate inclusion of PCPs in ACO contracting networks by multispecialty organizations. We calculated leakage rates both for primary care services provided specifically by PCPs and for the same set of office visits (CPT codes 99201-15, G0402, and G0438-9) provided by specialists. Of note, after the elimination of separate billing codes for outpatient specialty consultations effective January 2010, these consultations have been billed as office visits and are thus captured by this set of codes.11 Contract Penetration For each ACO, we summed all spending in 2010, including coinsurance amounts, for all services delivered in outpatient settings that were billed by ACO physicians (eAppendix in the Supplement). We then calculated the proportion of this spend940
ing that was devoted to beneficiaries assigned to the ACO as opposed to other beneficiaries receiving outpatient care from the ACO. To better reflect incentives for systemic changes in care delivery at the organizational level, we considered all of an organization’s member physicians, not just those included in its ACO contract, when assigning beneficiaries and totaling spending for the purpose of this measure. A sensitivity analysis using ACO contracting networks for this measure produced similar results. Patient Complexity and Per-Beneficiary Spending From Medicare enrollment files, we determined disability as the original reason for Medicare eligibility, presence of endstage renal disease, and receipt of Medicaid benefits. For each of 25 conditions in the Chronic Condition Warehouse,12 we determined if beneficiaries had been diagnosed with the condition before 2010. We also assessed total annual perbeneficiary spending in 2010 and 2011 for all services covered by Parts A and B of Medicare and the number of office visits for each beneficiary in 2010. Organizational Size and Primary Care Orientation We created 3 size categories for ACOs based on the number of assigned beneficiaries: (1) fewer than 2000 (or 45% of office visits provided by specialists). As detailed in Table 3, stability of assignment and leakage of office visits with PCPs varied considerably among ACOs but differed minimally by ACO size. Assignments were more stable for ACOs with greater primary care orientation. As expected, JAMA Internal Medicine June 2014 Volume 174, Number 6
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Table 2. Stability of Assignment and Leakage of Outpatient Care Among Medicare Beneficiaries Assigned to an ACO in 2010, Stratified by Beneficiary Characteristics Stability of Assignment
Leakage of Outpatient Care in 2010
Beneficiaries, No.
Assigned to Same ACO in 2010 and 2011
Office Visitsb With PCPs
430 658
80.4
8.7
66.7
0-2
93 944
73.4
7.8
63.1
3-5
149 179
82.2
7.9
65.9
6-8
116 642
82.9
8.8
67.0
≥9
70 893
81.9
10.2
68.9
Characteristic All beneficiaries assigned to an ACO in 2010
Office Visitsb With Specialists
CCW conditions present by 2010, No.
End-stage renal disease present by 2010 Yes
3978
69.3
11.1
61.0
No
426 680
80.5
8.7
66.8
Yes
86 409
75.3
10.6
65.7c
No
344 249
81.7
8.2
66.9c
Yes
79 143
76.4
10.7
67.5c
No
351 515
81.3
8.1
66.5c
Disability as original reason for Medicare eligibility
Medicaid recipient in 2010
Total spending in 2010 Lowest quartile
99 646
77.8
4.4
54.3
Quartile 2
111 083
82.5
6.7
64.2
Quartile 3
111 092
81.9
8.9
68.0
Highest quartile
108 837
79.1
11.3
68.1
42 909
76.6
11.9
67.5
Highest decile Office visitsb in 2010 With PCPs, No. 0
44 793
53.4
NA
32.6
1-2
124 521
76.4
4.1
70.9
3-5
147 185
86.7
6.7
71.4
≥6
114 159
87.2
10.5
71.6
0
64 078
82.0
5.1
NA
1-2
94 834
78.5
7.3
61.1
3-5
104 054
81.1
8.3
64.4
≥6
167 692
80.4
10.5
67.5
1-2
49 300
66.7
2.6
25.7
3-5
96 100
79.3
4.9
55.5
≥6
285 258
83.1
9.4
67.9
Abbreviations: ACO, Accountable Care Organization; CCW, Chronic Condition Warehouse; CPT, Current Procedural Terminology; NA, not applicable; PCP, primary care physician. a
Unless otherwise noted, data are reported as percentage of beneficiaries (stability) or office visits (leakage) among beneficiaries in the row category.
b
Outpatient primary care services as defined by rules for beneficiary attribution in the Medicare Shared Savings and Pioneer Program (CPT codes 99201-15, G0402, and G0438-9) .
c
Differences across beneficiary categories not statistically significant (P ⱖ .05).
With specialists, No.
With PCPs or specialists, No.
leakage of office visits with specialists was greater for smaller than larger ACOs (77.7% vs 63.6% [P < .001]) and for ACOs with specialty mixes oriented more toward primary care (95.6% for the highest quartile of primary care orientation vs 54.6% for the lowest quartile [P < .001]). Of Medicare spending on outpatient care billed by ACO physicians, 37.9% was devoted to ACO-assigned beneficiaries, varying from 24.6% at the 10th percentile of ACOs to 65.6% at the 90th percentile. This proportion varied minimally with size and was substantially higher for ACOs with specialty mixes oriented more toward primary care (60.0% for the highest quartile of primary care orientation vs 33.6% for the lowest quartile [P < .001]). 942
Discussion In this study of 145 organizations participating in the Medicare ACO programs, over one-third of beneficiaries attributed to an ACO in 2010 or 2011 was not assigned to the same ACO in both years. Thus, in any given year, a substantial share of patients for whom an ACO is held accountable may be newly or transiently assigned. Although healthy beneficiaries using little primary care contributed to this instability, unstably assigned beneficiaries were more likely than stably assigned beneficiaries to be in several high-cost
JAMA Internal Medicine June 2014 Volume 174, Number 6
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Enhancing Organizational Accountability in Medicare
Original Investigation Research
Table 3. Stability of Assignment, Leakage of Outpatient Care, and Contract Penetration Among ACOs With Specific Characteristicsa Stability of Assignment
Characteristic
ACOs, No.
Total
145
Leakage of Outpatient Care in 2010
Contract Penetration in 2010
Proportion of Patients Assigned to ACO in 2010 That Was Assigned to Same ACO in 2011
Office Visitsb With PCPs
Office Visitsb With Specialists
Proportion of Medicare Outpatient Spending Billed by ACO in 2010 That Was Devoted to Assigned Patients
80.4 (73.1, 77.1-84.3, 87.2)
8.7 (4.9, 6.7-10.3, 13.7)
66.7 (38.4, 56.7-89.9, 97.2)
37.9 (24.6, 33.2-55.2, 65.6)
Abbreviations: ACO, Accountable Care Organization; CPT, Current Procedural Terminology; IQR, interquartile range; PCP, primary care physician. a
Unless otherwise noted, data are reported as overall percentage (distribution across ACOs: 10th percentile, IQR, 90th percentile) of beneficiaries (stability), office visits (leakage), or spending (contract penetration) among ACOs in the row category.
b
Outpatient primary care services as defined by rules for beneficiary attribution in the Medicare Shared Savings and Pioneer Program (CPT codes 99201-15, G0402, and G0438-9).
c
Size categories by number of assigned beneficiaries are scaled to the entire traditional Medicare population.
d
Differences across beneficiary categories not statistically significant (P ⱖ .05).
e
Percentage of ACO office visits, as defined in footnote b, provided by PCPs.
Sizec Small,
